Field of the Invention
The invention relates to a device for decurling a web of material, such as a paper web, which device comprises:
a first main roller;
a second main roller arranged parallel to and at a distance of the first main roller, wherein the first main roller and the second main roller are arranged in a main plane; and
a decurling roller arranged parallel to and between the first and second main roller, when viewed in a direction perpendicular to the main plane.
Description of Related Art
When a web of material, such as in particular paper, is fed through a machine between a number of rollers and especially when the material is heated on the way, such as in a printer, the web of material tends to curl.
The curling of the web of material complicates further handling of the material. Therefor, decurling devices are known to ensure that the web of material is outputted more or less flat.
For example U.S. Pat. No. 5,580,044 discloses a decurler. In this decurler two conveyor belts are placed against each other, such that a web of material can be transported between the two conveyor belts.
In the zone where the conveyor belts parts are adjacent each other, three rollers are placed alternately above and below this zone, such that path of the web of material can optionally be distorted into a zig zag path. By controlling the amount of distortion of the path, the amount of decurling can be set.
The construction of this device with two opposed conveyor belts and three rollers, which need to be set separately to control the decurling is complicated and therefor also expensive.
Furthermore, the diameter of the rollers cannot be decreased at will, as a smaller diameter will cause the roller to bend more easily by the tension in the web of material, such that the decurling effect is not equal over the width of the web of material. This will result in the edges of the web of material to curl up, while the center will be flat. However, the smaller the diameter of the decurling roller, the better the decurling effect will be under the condition that the decurling roller does not bend.
Finally, because the web of material is positioned between two conveyor belt, speed differences could occur between the two conveyor belts and the web, such that the web is damaged.